Therein lies one of the big problems, in a best case scenario Europe would have the virus controlled by summer so you could justify travel within the EU & possibly Russia β but what about Africa, the Caribbean or Turkey although apparently they have just started their own vaccination program (using the Chinese variation). so who knows?
Travel corridors didn't work last summer so the only sensible option is to cancel all foreign travel for a minimum of 5 years and the Tokyo Olympics, World Cup, and all international sport apart from cricket π (cos it's good - despite England doing well today) and cycling π΄ (cos they're all on drugs and used to fellow competitor's going AWOL on a semi-regular basis).